Today, many modern manufacturing facilities extensively utilize modular conveyor systems to transport articles to and from various work stations during all stages of production. In recent years, manufacturers using production lines with conveyors as an integral component of the material handling system have realized reasonably significant gains in productivity and resource utilization. As a result, modular conveyor systems have become even more widely implemented and have been adapted to meet an even wider scope of the material handling needs of producers of a multitude of consumer and industrial goods. Therefore, the continual development of improved modular conveyors is necessary to keep pace with the demands and expectations of the users of such conveyors.
Conventional conveyor systems employing endless, modular link belts or chains are typically driven at one end of an elongated guide structure, frame or “bed” supported above the ground. The force for driving the belt or chain is transmitted from a motive device, such as a variable speed electric motor, to a rotating drum or a plurality of gang-driven sprockets coupled to a rotating drive structure, such as a shaft. At the opposite end of the guide structure or bed, idler sprockets are coupled to a freely-rotating idler shaft or drum. As should be appreciated, these structures assist in supporting and guiding the endless belt or chain as it makes the transition from the forward run to the return run, or vice versa, at each respective end of the guide structure. Intermediate drive units, including frictional drives, may also be used in place of or in addition to the end drive unit.
Oftentimes, a plurality of laterally repeating modular links, or unitary link sections comprising a plurality of laterally repeating link-shaped structures (collectively referred to as “links”), form the conveyor chain or belt. The links are typically formed of a low-cost, high strength, wear resistant material, such as Acetal or UHMW polypropylene. To form the chain or belt, a plurality of links or link sections are positioned in interdigitating, longitudinally repeating rows. Each row is then connected to the adjacent row by a transverse connecting rod that projects through one or more apertures in a first, usually leading portion of a first link or link section and one or more apertures or slots in a second, or trailing portion of the next-adjacent link or link section. At both lateral ends of each row, special side links are used that include slots for receiving a locking structure, such as a tab, that retains the transverse connector rod in place. Examples of this type of arrangement are found in commonly assigned U.S. Pat. Nos. 4,953,693 and 5,031,757, the disclosures of which are incorporated herein by reference. Due to their low-cost, adaptability and long service life, chains or belts formed in this fashion have gained widespread acceptance among those seeking conveying solutions.
In the past, others have recognized the potential value of a “micropitch” chain formed of a plurality of interconnected links, but capable of behaving almost like it is formed of a continuous piece of material, such as a belt formed of a piece of rubber or fabric. An example is found in U.S. Pat. No. 5,967,296 to Dolan, which discloses a belt including a plurality of link sections including laterally and longitudinally offset spherical beads having apertures for receiving a plastic transverse connector rod. Once inserted through the aligned apertures in a pair of interdigitated link sections, both ends of the connector rod are mutilated, such as by melting. This captures the rod in place between the link sections to form a belt section. One improved version of a micropitch chain that advantageously avoids the need for separate connector rods is found in Applicant's co-pending application Ser. No. PCT US03/05666, which is incorporated herein by reference.
Modular conveyor systems often include two or more conveyors strategically positioned in an end-to-end relationship so as to move articles along a feed path in a conveying direction. This type of arrangement is especially beneficial in the food processing or packaging industries, and where space availability is sometimes limited. However, a prevalent problem with such an end-to-end conveyor system is the lack of a compact, driven transfer conveyor including a belt or chain that efficiently and effectively provides for the smooth transition of articles along a transfer zone established between the ends of the adjacent conveyors.
In this regard, the '296 patent to Dolan proposes the use of a small pitch chain in a transfer conveyor in which the driving force is provided by a smooth surface drive roller, as opposed to a sprocket. However, the combined requirements of a separate electric motor for driving the belt associated with the transfer conveyor and a complicated, non-reversible tensioning assembly are deleterious, since these features increase not only the space requirements, but also the manufacturing and maintenance expense.
Accordingly, a need is identified for an improved, conveyor with self-tensioning capabilities that may be used for efficiently and effectively conveying articles, including between the ends of two adjacent conveyors at a transfer location.